Processing tools used in the semiconductor industry have developed into complex processing systems having a number of associated process modules. Due at least in part to this development trend, the dividing line between the tool control systems and the factory control systems are becoming increasingly blurred. The factory system can allow the tool control system to control certain segments of the process sequence. This can create new opportunities for tailored control and optimization of segments of the process sequence on a lot-to-lot basis or even on a wafer-to-wafer basis, but new challenges can also be created. If the factory control system cedes control over the wafers to the tool platform, then it also must cede direct knowledge of what actually happens to the wafers to the same platform. As a result, a new architecture should be created for the integration of the tool platform with the factory control system. The new architecture would require the tool platform to report what happened to the wafers including recipes, measured data, events, exceptions, etc. The new architecture must require the factory system to set up a framework to be followed by the tool platform including process limits, allowable conditions and required response to exceptions.
In addition, multi-module tools need to interface with factory systems that adhere to Semiconductor Equipment and Materials International (SEMI) standards.
Data from multiple events performed in a particular module, which need to be reported to the factory system, can be written by the controller of the tool platform or by the factory system controllers upon a subsequent visit of the wafer to the same module. One limitation of this arrangement is that recipes cannot be associated with the physical module because the physical module is used more than once. Moreover, the physical module may perform different operations.
One way to resolve this problem is to find a way for the factory and tool information systems to deal with multiple passes to the same module in a multi-chamber process tool. In addition, for a multi-chamber system having the problem of establishing routing that may be different for each wafer (wafer sampling) and/or establishing a dynamic routing which is determined by the tool (again including wafer sampling), a secondary solution is required. In particular, demand has developed for an information systems architecture that is able to function when each module samples the wafers differently, when the wafers can make more that one pass through a physical module, and when the tool can change the sequence or sampling.
For semiconductor processing, it is well-established that feedforward controllers may be used in the fabrication of semiconductor integrated circuits by semiconductor manufacturing facilities (fabs). Until recently, wafers were treated as a batch or a lot and the same processing was performed on each of the wafers in the lot. The size of the lot varies depending on the manufacturing practices of the fab but is typically limited to a maximum of 25 wafers. Measurements were routinely made on a few wafers in the lot and adjustments were made to the processing based on these sample measurements. This method of control which is based on sample measurements on the current lot and process recipe adjustments for ensuing lots is called lot-to-lot control (L2L). The process models and information necessary to modify the process recipes for L2L control were stored and the computations were performed at the fab level. Recently manufacturers of semiconductor processing equipment (SPE) have included the ability to measure each wafer immediately before and after the processing is performed. The capability to measure each wafer on the processing tool is called integrated metrology (IM). IM, in turn, enabled the ability to measure and adjust the process recipe at the wafer-to-wafer (W2W) level. Because of the high volume of data collected and the short period of time between the measurements and subsequent processing of the wafer, it may be necessary to provide the ability to perform wafer-to-wafer (W2W) control at the tool rather than at the fab level.